The production of polyurethane or polyisocyanurate foams by foaming foamable reaction mixtures based on polyisocyanates, compounds having reactive hydrogen atoms, blowing agents, stabilizers and optionally further additives is operated on a large industrial scale today. An important field of use of these foams is insulation, in particular thermal insulation. To produce insulating foams, it is necessary to produce rigid foams having a relatively low foam density of <50 kg/m3 and, as an essential criterion, a very large number of small closed cells (high cell density).
A blowing gas is necessary for such a foam to be able to form. Conventional blowing agents here are hydrocarbons, (partially) halogenated saturated and unsaturated hydrocarbons and also substances which generate CO2.
Apart from the capability of forming many small, homogeneous closed cells during foaming, preferred blowing agents have a low gas-phase thermal conductivity and also a low Global Warming Potential (GWP). In this context, unsaturated halogenated hydrocarbons, known as HFO blowing agents, have been able to be identified as particularly effective blowing agents. The use of HFO blowing agents for producing polyurethane foams is, for example, described in the documents    EP 2154223 A1, EP 2197 935 B1 and US 2009/0305875 A1.
Despite the demonstrated effectiveness of unsaturated halogenated hydrocarbons as blowing agents, a disadvantage of these substances is that they are often only insufficiently miscible with the polyurethane system to be foamed or with the basic raw materials used for PU foam production. This leads to mixtures of this type having only a low storage stability and frequently tending to undergo phase separation into two or more phases, which can lead, inter alia, to defects in the PU foam obtained.
Particular importance is attached to the separation stability of the polyurethane systems or polyol mixtures when using preformulated polyurethane systems in the production of insulation materials for cooling appliances (refrigerators and upright freezers or freezer chests). Here, it is customary to mix the blowing agent before foaming with the so called A component which consists of, in addition to the blowing agent, one or more polyols, one or more catalysts, foam stabilizers, water, optionally flame retardants and optionally further additives and auxiliaries. This is mixed during foaming with the so called B component, which generally consists of an isocyanate, usually polymeric MDI, to which no additives have been added, and foamed. To make a trouble-free foaming process possible, it is necessary for the A component to have a sufficient separation stability so that no undesirable demixing phenomena which could lead, as described above, to foam defects occurring during foaming.
In addition, a trouble-free production process can be ensured by a sufficient storage stability of a preformulated A component in a large-scale industrial foaming process. In this way, it is possible, for example in the case of relatively long plant downtimes, e.g. during maintenance work or over the weekend, to avoid separation of the system in lines and stock vessels which would inevitably lead to severe foam defects when the plant is started up again.
It was therefore an object of the present invention to provide a composition containing at least one polyol component, at least one blowing agent which is characterized in that it is an unsaturated halogenated hydrocarbon, a catalyst which catalyzes the formation of a urethane or isocyanurate bond and optionally further additives, where the composition is characterized in that it is separation-stable for at least three days.
To achieve solubilization between polyol systems and blowing agents, the use of various surfactants has been proposed in the past.
WO 2007/094780 describes polyol mixtures containing hydrocarbons as blowing agents, with an ethoxylate-propoxylate surfactant being added to the mixtures to improve the solubility of the blowing agent in the mixture.
U.S. Pat. No. 6,472,446 describes polyol mixtures containing hydrocarbons as blowing agents, where a butanol-initiated propylene oxide polyether surfactant is added to the mixtures to improve the solubility of the blowing agent in the mixture.
WO 98/42764 likewise describes polyol mixtures containing hydrocarbons as blowing agents, where a C12-C15-initiated polyether is added as surfactant to the mixtures in order to improve the solubility of the blowing agent in the mixture.
WO 96/12759 likewise describes polyol mixtures containing hydrocarbons as blowing agents, where a surfactant which has an alkyl radical having at least 5 carbon atoms is added to the mixtures to improve the solubility of the blowing agent in the mixture.
EP 0767199 A1 describes the use of diethanolamides of fatty acids of natural origin as surfactant for producing polyol mixtures which have hydrocarbons as blowing agents.
EP 1520873 A2 describes mixtures of halogenated hydrocarbon blowing agents and blowing agent reinforcers which have a molecular weight of less than 500 g/mol, with the blowing agent reinforcers being able to be polyethers or monoalcohols such as ethanol, propanol, butanol, hexanol, nonanol or decanol. The ratio of blowing agent to blowing agent reinforcer is said to be 60-95% by mass: 40-5% by mass. However, the halogenated hydrocarbons used are not HFO blowing agents. In addition, this document does not disclose whether the blowing agent reinforcers used lead to compatibilization of the blowing agent in polyols.
WO 2013/026813 describes microemulsions of polyols and nonpolar organic compounds, which are obtained by use of at least one halogen-free compound which contains at least one amphiphilic compound selected from among non-ionic surfactants, polymers and mixtures thereof and at least one compound different from this compound, and their use in the production of polyurethanes. The nonpolar compounds used can also contain proportions of fluorinated compounds. Polyol-based microemulsions which contain exclusively halogenated nonpolar compounds are not described in this document.
Since the dissolution properties of halogenated hydrocarbons differ fundamentally from those of nonfluorinated hydrocarbons, it is not possible to apply the additives proposed for hydrocarbon-based blowing agent to the present problem.